东准噶尔老爷庙地区碱性花岗岩锆石U- Pb定年、地球化学及其地质意义
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注: 本文为中央返还新疆两权价款“新疆巴里坤县1∶50000 L46E020016、L46E020017、L46E021015、L46E021016、L46E022015、L46E022016 六幅区域地质调查” (编号:T15-1-LQ01)的成果。


Zircon U- Pb Dating, Geochemical Characteristics of Alkali- granites in Laoyemiao Area, Eastern Junggar, and Geological Significance
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    摘要:

    老爷庙地区位于东准噶尔东部,是中亚造山带的重要组成部分。老爷庙碱性花岗岩具有高硅(SiO2 63.58%~69.92%);富碱(Na2O+K2O 9.38%~9.81%)、贫钙(CaO 0.44%~2.47%)、低钛(TiO2 0.52%~0.97%)的特征,与典型A型花岗岩相似,成因类型上属A2型花岗岩,产于后造山环境。富集大离子亲石元素Rb、Ba、K、Th及高场强元素Zr,相对亏损P、Ti、Nb、Ta。轻稀土富集明显(LREE/HREE=7.62~8.31),且轻稀土元素内部分馏相对较强,重稀土元素元素内部分馏较弱,弱的Eu负异常(δEu =0.52~0.91)。锆石温度饱和温度819~890℃,属于高温花岗岩,中等压力。LA-ICP-MS 锆石U-Pb年龄显示其结晶年龄为两期,分别为(297.0±6.5)Ma和(310.0±2.0)Ma,表明其形成时代为晚石炭世—早二叠世。综合本文数据及区域地质特征,老爷庙地区在早二叠世早期(297.0±6.5)Ma时已经拼贴到西伯利亚板块,进入后造山向板内转化的过渡期,结束了该地区地壳的侧向增生,但由于大量幔源岩浆底侵到下地壳,使该区仍在垂向增生。

    Abstract:

    Objectives: Laoyemiao area is located in east of East Junggar,known as the important tectonic metallogenic belt of the Central Asian Orogenic Belt(CAOB). Through high- precision zircon U- Pb dating and comprehensive research on rock geochemistry, combined with regional comparison, the diagenetic age was determined and its formation environment was discussed to provide chronology and petrogeochemical constraints for the study of Late Paleozoic tectonic magmatism. Methods: The full analysis of the rock was tested in the Aussie Minerals Laboratory in Guangzhou. After the sample was crushed, shrunk and ground to 200 mesh, the content of rare earth elements was determined by MEMS81 fusion inductively coupled plasma mass spectrometry. ME- XRF26X fluorescence spectrometer was used for precise analysis. Determination of iron oxide by the main trace element of rock and Fe- VOL05 titration. Zircon single minerals were selected in the laboratory of the Institute of Regional Geology and Mineral Resources Research ofHebei Province, and the target, CL photographing, transflective photography, zircon dating and data were carried out in the State Key Laboratory of Mineral Deposits Research Mechanism of Endogenous Metal Deposits, Nanjing University. Correction. The zircon U- Pb test was carried out on an Agilient 7500a ICP- MS connected by a 193 nm laser sampling system. The laser ablation beam spot diameter was 32 μm and the frequency was 6 Hz. He gas was used as the carrier gas for the ablation material, and then mixed with the Ar gas. Analyze. The isotope ratios obtained by the experiment were processed by the GLITTER program and subjected to ordinary lead calibration. The test results are shown in Table 2. The age harmonic curve and the weighted average calculation were processed using Isoplot (3.0) software. Results: Laoyemiao alkali granites are characterized by high SiO2 (63.58%~69.92%), high alkaline(Na2O+K2O: 9.38%~9.81%), low CaO (0.44~2.47%) and low TiO2(0.52~0.97%), Similar to typical A- type granites, which genesis type belongs to the A2- type granites and produced in the post- orogenic environment. The alkali granites are enriched Rb、Ba、K、Th、Zr and relatively depleted in P、Ti、Nb、Ta. Obvious enrichment light rare earth elements(LREE/HREE=7.62~8.31), the internal fractionation of light rare earth elements is relatively strong, but weak in heavy rare earth elements , and lack in Eu anomaly(δEu =0.52~0.91).Zircon temperature saturation temperature of 819~890℃, belonging to hightemperature granite,moderate pressure. The zircon UPb age of LAICPMS shows that its crystallographic age is two phases, which are (297.0±6.5) Ma and (310.0±2.0)Ma, respectively, indicating that the age of its formation is Late Carboniferous. Conclusions: Laoyemiao area was tiled into the Siberian plate at the end of the Late Carboniferous period (297.0±6.5) Ma and entered the transitional period of post- orogenic conversion into the plate.The lateral growth of the crust in the area was ended, but the area was still vertically proliferated due to the intrusion of a large amount of mantlederived magma to the lower crust.

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熊双才,张征峰,李广,刘润泽,华叙登,赵富庄,周鹏飞,李关禄.2019.东准噶尔老爷庙地区碱性花岗岩锆石U- Pb定年、地球化学及其地质意义[J].地质论评,65(1):221-231,[DOI].
XIONG Shuangcai, ZHANG Zhengfeng, LI Guang, LIU Runze, HUA Xudeng, ZHAO Fuzhuang, ZHOU Pengfei, LI Guanlu.2019. Zircon U- Pb Dating, Geochemical Characteristics of Alkali- granites in Laoyemiao Area, Eastern Junggar, and Geological Significance[J]. Geological Review,65(1):221-231.

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  • 收稿日期:2018-04-03
  • 最后修改日期:2018-12-13
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  • 在线发布日期: 2019-01-19
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